1. Field of the Invention
The present invention relates to surgical instruments, and, more particularly, to trocars which are used to pierce or puncture an anatomical cavity to provide communication with the inside of the cavity during a surgical procedure.
2. Description of the Prior Art
Endoscopic surgery, and in particular laparoscopic surgery, constitutes a significant method for performing surgeries and has become the surgical procedure of choice, because of its patient care advantages over xe2x80x9copen surgery.xe2x80x9d In particular, a significant advantage of laparoscopic surgery over open surgery is the decreased post-operative recovery time. In most instances, a patient is able to leave the hospital within hours after laparoscopic surgery has been performed, as compared to the multi-day hospitalization necessary to recover from open surgical procedures. Further, laparoscopic surgery provides decreased incidents of post-operative abdominal adhesions and decreased post-operative pain. Cosmetic results are also enhanced with laparoscopic surgery.
A trocar is an essential medical instrument for use in laparoscopic surgery, because it is used to puncture the wall of an anatomical cavity. A trocar includes a tube or cannula and a sharp, generally pointed cutting element called an obturator. The obturator fits within the cannula and has a sharp piercing tip at its end.
Conventionally, a laparoscopic trocar insertion procedure is preceded by the insufflation of the abdominal cavity with carbon dioxide. The introduction of this gas into the abdominal cavity lifts the abdominal wall away from the internal viscera. The abdominal wall is then penetrated with the trocar, and after insertion of the trocar through the abdominal wall, the obturator is removed by the surgeon, leaving the cannula or tube protruding through the body wall. Laparoscopic instruments can then be inserted through the cannula to view internal organs or to perform surgical procedures.
Penetrating the wall of the abdominal cavity with the trocar is done relatively quickly, and while the obturator encounters a fair amount of resistance from the skin muscle and tissue membranes of the abdominal wall, the resistance to the trocar drops quickly once the cutting element passes through the abdominal wall. Within the abdominal cavity, the sharp point of the cutting element may easily injure or cut an internal organ upon the slightest of contacts. Accordingly, many trocars include a safety shield that snaps forward to cover the sharp point of the obturator, once the trocar has penetrated the abdominal wall. Preferably, the safety shield is locked into place once the abdominal wall has been penetrated, and cannot be unlocked absent positive intervention by the surgeon.
While locking safety shields for trocars have been available, the locking mechanisms employed in these trocars has suffered from the disability that consistent pressure is not placed on the safety shield. Further, the architecture of locking mechanisms in the prior art trocars has not been open, which has made those trocars difficult to sterilize.
Despite the fact that trocars are hand-held instruments, prior art trocars have been less than ergonomically friendly to the user. Rather, prior art trocars have suffered from the disability of being difficult to control, since they are not designed to provide for a plurality of hand positions or for different holding levels that allow for different size hands to manipulate the trocar.
The foregoing and other shortcomings of prior art trocars have been overcome by the trocar of the present invention.
A trocar in accordance with the present invention comprises a body assembly, a cannula assembly, and an obturator assembly. The cannula assembly includes an outer cannula which is attached to the body assembly to define a bore therethrough and an inner cannula inserted in said bore. The inner cannula has proximal and distal ends, has a length which is greater than the length of the outer cannula, and may move axially from an extended position to a retracted position. The inner cannula serves as a safety shield for the obturator.
The trocar body includes an inner cannula control mechanism having a locked position and an unlocked position which is activated during surgical insertion of the trocar. This control mechanism includes a mounting mechanism which is attached to the trocar inside the body assembly to prevent rotation of the inner cannula, and axial movement of the inner cannula in the locked position. The inner cannula control mechanism also includes a trigger mechanism for placing the safety shield control mechanism in the unlocked position to allow limited axial movement of the inner cannula.
A trocar in accordance with the present invention also includes an obturator assembly in the bore of the trocar. The obturator has a sharp end which is shielded by the inner cannula when the inner cannula control mechanism is in the locked position. The sharp end of the obturator becomes exposed during surgical insertion of the trocar when the inner cannula control mechanism is in the unlocked position and the inner cannula is retracted.
The mounting mechanism in the inner cannula control mechanism includes a mounting bracket having vertical ribs and the inner cannula has axial slots for engagement with said vertical ribs to prevent rotation of the inner cannula. The mounting mechanism also has a locking arm assembly comprising two independently spring-loaded locking arms for engaging the proximal end of the inner cannula to prevent axial movement of the inner cannula in the locked position.
The trigger mechanism of the safety shield control mechanism includes apparatus for moving the locking arm assembly to an unlocked position to allow limited axial movement of the inner cannula toward the rear of the trocar. In a preferred embodiment the trigger mechanism comprises a plunger-like button shaft which extends from the outside of the trocar body to the inside of the trocar body. The portion of the button shaft which is outside the trocar body has an end for threaded engagement with a spring-loaded cap. The portion of the button shaft on the inside of the trocar body has a tapered end which is slidably engaged in a hole in the locking arm assembly to move both arms of the locking arm assembly to the unlocked position when the spring-loaded cap is depressed. As the inner cannula retracts during surgical insertion of the trocar, a pin on the inner cannula separates the two locking arms. When the trocar passes through the abdominal wall of the patient, a spring forces the inner cannula into the extended position and one of the locking arms snaps back and engages the inner cannula to lock it in the extended position.
A trocar in accordance with the present invention also includes a spring-loaded flapper valve assembly which is located inside the trocar body assembly at the rear of the trocar body assembly. This flapper valve assembly closes to seal the bore of the trocar when the obturator assembly is removed from this trocar.
A trocar in accordance with the present invention is fabricated to provide two holding levels to accommodate different size hands.